This application claims priority of Taiwanese Application No. 091211330, filed on Jul. 24, 2002.
1. Field of the Invention
The present invention relates to a wood planing machine, more particularly to a wood planing machine with an error reducing unit for a workpiece thickness to be removed.
2. Description of the Related Art
Referring to FIGS. 1 to 3, a conventional wood planing machine 10 is shown to include a base 11 having left and right sides, left and right pairs of posts 12 extending uprightly from the left and right sides of the base 11, a cutter carriage 13 having left and right carriage ends 131 mounted slidably and respectively on the left and right pairs of posts 12, and left and right screw rods 16 mounted rotatably on the left and right sides of the base 11. Tubular left and right threaded members 15 extend through two through holes in the left and right carriage ends 131. The left and right screw rods 16 extend through and threadedly engage the threaded members 15, respectively. Left and right fastening nuts 19 threadedly and respectively engage the threaded members 15 so as to secure the threaded members 15 on the cutter carriage 13. A transmission unit 18 includes two sprockets 181 fixed to lower ends of the left and right screw rods 16, and a transmission chain 182 trained on the sprockets 181 so as to permit synchronous rotation of the left and right screw rods 16, which, in turn, results in vertical movement of the cutter carriage 13 relative to the base 11. A handle 17 is mounted on a top end of the right screw rod 16 to facilitate turning of the left and right screw rods 16.
Referring to FIG. 4, the cutter carriage 13 is parallel to the base 20, and the threads 150 of the threaded members 15 rest on the threads 160 of the screw rods 16 due to the weight of the cutter carriage 13. Thus, clearances 161 are formed between the threads 150 of the threaded member 15 and the threads 160 of the screw rods 16. As such, the threaded members 15 and the carriage 13 can move relative to the screw rods 16, thereby resulting in an increase in error for workpiece thickness that is to be removed.
Therefore, the object of this invention is to provide a wood planing machine with an error reducing unit that can prevent movement of a cutter carriage relative to a set of upright screw rods.
Accordingly, a wood planing machine of the present invention includes: a base having four corners; four hollow posts extending uprightly from the corners of the base, respectively, each of the posts being formed with an axial slot for access to an interior thereof; four screw rods extending rotatably and uprightly from the corners of the base through the posts, respectively, each of the screw rods having an externally threaded portion that is formed with an external thread; a cutter carriage having four corners mounted respectively, vertically and slidably on the posts, and a horizontal bottom surface; a transmission unit connected to the screw rods to permit synchronous rotation of the screw rods; and an error reducing unit including four tubular threaded members that are secured respectively to the four corners of the carriage, that are disposed respectively within the posts in such a manner that the threaded members are exposed from the axial slots in the posts, and that define axially extending threaded bores respectively engaging the screw rods such that rotation of the screw rods results in movement of the carriage along the posts. Each of the threaded members has an internally threaded portion defining a respective one of the axially extending threaded bores and engaging the externally threaded portion of the respective one of the screw rods 50, and a circumferential slot formed through a wall of the internally threaded portion so as to divide the internally threaded portion into an upper part and a lower part. The upper part is disposed above the circumferential slot, and has a bottom surface that defines a top end of the circumferential slot. The lower part is disposed below the circumferential slot, and is formed with a vertically extending threaded bore therethrough. Each of the upper and lower parts is formed with an internal thread that engages the external thread of the respective one of the screw rods. The error reducing unit further includes four locking bolts that engage respectively the vertically extending threaded bores in the threaded members and that press against the bottom surfaces of the upper parts of the internally threaded portions of the threaded members such that the internal threads of the upper parts of the threaded members press upwardly against the external threads of the screw rods and such that the internal threads of the lower parts of the threaded members press downwardly against the external threads of the screw rods so as to lock the internally threaded portions of the threaded members on the externally threaded portions of the screw rods.